Method of making sheet-metal roof coverings and roof covering made in accordance with this method



Nov. 21, 1967 s. o. GRGNLUND 3,353,319

METHOD OF MAKING SHEET-METAL ROOF COVERLNGS AND ROOF COVERING MADE IN ACCORDANCE WITH THIS METHOD Filed Oct. 19, 1965 INVEN TOR. SVf/V 0,4 0; @ea'kvz (/Aw United States Patent 3,353,319 METHOD OF MAKING SHEET-METAL ROOF COV- ERINGS AND ROOF CGVERING MADE IN AC- CORDAN CE WITH THIS METHOD Sven Ulof Griinlund, Skara, Sweden, assignor to Rostfria Tak AB, Fagersta, Sweden, a corporation of Sweden Filed Oct. 19, 1965, Ser. No. 497,650 Claims priority, application Sweden, Oct. 3, 1960, 9,434/60; June 15, 1961, 6,271/ 61, 6,272/61 8 Claims. (Cl. 52520) The present invention is a continuation-impart of my copending US. patent application Ser. No. 142,202 filed on Oct. 2, 1961, now abandoned and having the title Method of Making Sheet-Metal Roof Coverings and Root Covering Made in Accordance With This Method.

The invention has for its purpose to obtain a roof covering which is tight, requires no maintenance, enable-s simple roof structures and is esthetic as to its appearance. The material of the roof covering consists of strips or pieces of stainless steel preferably manufactured by cold rolling. Though the price per unit of weight of stainless steel is comparatively high, a roof covering made from such material has been possible due to a certain combination of steps and features of construction which are characteristic of the invention.

It belongs to the known art to use stainless steel in covering structures forming parts of railway cars and the like. However, such structures are adapted to receive mechanical stresses requiring a relatively thick material which is bent in a suitable manner, for example to form corrugations, with a view to augmenting the resistance of the structure. On the other hand, it is not known to use stainless steel as a material for conventional roof covering which has for its single object to protect the underlying structure against exposure to the elements.

The starting material used for the present roof covering and the method of making such roof covering is sheet material, preferably strips of stainless steel of an austenitic or ferritic composition. The stainless material has a high strength whereby a sheet material of less thickness can be used as compared with that of galvanized sheet iron and sheet copper. The maximum thickness of the sheet stainless steel need only be 0.5 mm., and the usual thickness is 0.3 mm. or even less. The stainless material will become stiffened to a high extent by cold-working (for example bending or folding) so that it is advantageous to limit the thickness of the material also for this reason in connection with the present method which relates to continuous welding and folding by means of self-sustained manual apparatus. The coeflicient of expansion of the austenitic stainless steel is about 60% higher than that of conventional iron. Due regard to this must be given in dimensioning joints between strips forming a roof covering. This is effected by due attention to the angle to which marginal portions of the strips to be joined are bent up to form flanges suitable for joining.

The flanges of the strips formed by bending up the longitudinal margins thereof are united by electric welding, preferably electric resistance welding. Alternatively, heating by induction may be employed. The weld is placed at a distance from the edge of the flanges or of the highest flange to such an extent, e.g. 5-l5 mm., preferably 8 to 12 mm., that the flanges can be folded above the weld. As a result, it is possible to compensate for the shrinkage to which the marginal portion undergoes during by the welding operation so that the flange will remain straight.

The flanges to be united should be pressed together during the Welding operation, as they form an angle with one another. It is also important to limit the width of the weld and to locate it at a distance from the edges of the flanges. Preferably, roll electrodes are used for the resistance welding operation.

The angle through which the flange parts are to be turned up is chosen with regardto the above-mentioned thermal expansion as well as to a suitable performance of the welding operation. It has been found that this angle should be less than 87 and more than Accordingly, the turned-up flange parts of two adjacent strips of sheet to be joined make an acute angle less than 30.

If the angle between the flange parts is less than 30, the welding operation may be carried out by electric resistance welding by means of a roll welding machine which is moved along the flanges of the sheets. In this case, the flanges can be sufficiently pressed against each other without the use of too great force so as to obtain a satisfactory weld, in spite of the fact that the weld joint is placed somewhat below the top edges of the flanges. Such a location of the weld joint has proved suitable if a roll welding machine is used, because if the welding electrodes (welding rolls) are moved along quite close to the top edge, fused material from the sheet may adhere to the welding rolls and derange the continued welding operation.

Another advantage resulting from the indicated oblique position of the flange parts relative to the body of the strips is the formation of a wedge-shaped space between the flanges which can be used for receiving fastening members for anchoring the sheet to the underlying supporting structure. Such anchoring devices are necessary in order to maintain the roof covering in a uniplanar position on the roof in spite of the movements resulting from thermal expansion and contraction of the sheets. Suitably an anchoring member is secured to the weld joint, prefer-ably in the form of a strip having a bent lower part in displaceable engagement with a corresponding anchoring member which is suitably secured to a piece of sheet fastened down to the underlying roof structure.

Welding of the strips is a suflicient measure to obtain a tight and reliable joint, provided that the Welding operation is carried out in a suitable manner. To prevent penetration of moisture and dust between the flange parts above the weld which could cause corrosion, the weld is doubled over, resulting in a very tight and durable joint. Furthermore, it is of importance to avoid the sharp edges which otherwise would be formed by the cut top edges of the upstanding flanges of the relatively hard and thin sheet steel. A further advantage of the folding is that the combined flanges are given an increased stiffness.

The doubling operation may be effected with flanges of equal height which are folded together over to one side of one flange. But the flanges may also be unequal so that one is higher than the other one. When the strips of sheet are placed close to each other, the higher flange part will project above the lower one and can readily be turned over the lower flange part after the welding operation has been completed. As a result, the welding operation can be carried out by electric resistance welding by means of a roll welding machine. The doubling operation, too, can be carried out continuously by a folding machine.

The invention is described in greater detail with reference to embodiments thereof illustrated in the accompanying drawing in which FIG. 1 is a perspective view of a sheet covering. FIGS. 2 and 3 are vertical sectional views of a longitudinal seam provided in accordance with the invention between two pieces of sheet before and after the welding operation, respectively. FIG. 4 is a vertical sectional view of a final seam at an anchor. FIGS. 5 and 6 illustrate a special embodiment comprising both welding and doubling of the joint, FIG. 5 being a vertical sectional view of a pair of adjacent pieces of sheet before the joining operation, and FIG. 6 illustrating the pieces of sheet after welding and doubling.

The roof covering illustrated consists of strips such as and 11 of stainless steel which are joined to each other by means of longitudinal seams 9, FIG. 1. Preferably, the strips extend from the ridge 4 to the lower edge 5 of the roof. The seam 9 is shown in detail in FIGS. 2 to 4.

In FIG. 2 there are shown two adjacent strips 10 and 11 having turned-up flanges 12 and 14, respectively, of equal height. The flanges make an angle of about 85 with the base, and between them there is formed a wedgeshaped space 18 which permits thermal expansion of the strips 10 and 11 without buckling and also provides a space for means for fastening the strips to the base. After the welding operation by means of a roll welding machine, the space 18 remains between the free intermediate parts 16, 17 of the flanges 12, 14. The fastening means comprises an angle member 19 (FIG. 4) secured to the base and a strip of sheet 20 the upper end of which is connected to flanges through the weld joint and the lower end of which is turned up to form a hook displaceably engaged by a lower member in the form of a correspondingly turned-down hook-shaped part of the angle 19 which in turn is secured, such as by welding, to a piece of sheet 21 fastened to the underlying roof covering support 8. The piece of sheet 21 suitably extends equally long on both sides of the joint and may throughout the entire length of the joint serve as well as a sliding surface for the joined strips 10 and 11, thereby facilitating the movements of these sheets upon thermal expansion and contraction on account of changes in temperature. Fastening members of this type are suitably spaced apart longitudinally of the length of the joint. The weld joint 15 extends lengthwise of the longitudinal seam 9 and is spaced a substantial distance below the cut edges of the turned-up flange parts 12 and 14. After welding, both flange parts located between the weld 15 and the top of the flanges are folded to one side to cover the weld at this side, whereby sharp upstanding edges are avoided and the combined flanges are given an increased stiffness.

FIG. 5 illustrates a pair of adjacent strips of sheet 10, 11 intended to be joined together by welding as well as folding or doubling. The flange 12 is higher than the flange 14. While the flanges are urged against each other, they are welded together, suitably by means of a roll welding machine such that the weld joint (15 in FIG. 6) is placed below the cut edge of the lower flange 14.

After the welding operation, the projecting marginal portion of the flange 12 is folded down over the flange 14, as shown in FIG. 6. This conventional doubling operation may be carried out by means of a folding machine.

In the embodiment illustrated in FIGS. 5 and 6 the covering sheet should be anchored to the base in a manner corresponding to that shown in FIG. 4.

What I claim is:

1. A method of making roof coverings from sheet metal, comprising the steps of using strips of stainless steel having a maximum thickness of 0.5 mm., bending marginal portions of such strips through an angle of less than 87 and more than 75 to form upstanding flanges, placing the strips adjacent one another with the flange of one strip adjacent a flange of another strip, pressing the adjacent flanges together by means of pressure rolls, electric resistance welding the pressed flanges together while placing the weld at a distance from the edges of the flanges, and folding over that part of the welded flanges which is located between said edges and the weld.

2. A method of making roof coverings from sheet metal, comprising the steps of bending up marginal portions of strips of stainless steel of a thickness less than 0.5 mm. through an angle of less than 87 and more than one strip being bent to obtain a flange of greater height than a flange bent up on another strip, placing strips with flanges of different heights adjacent one another to locate said flanges adjacent One another, pressing the flanges together by pressure rolls and simultaneously electric resistance welding the flanges together while placing the weld in spaced relation below the edge of the lowest flange, and folding the highest flange over and on the lowest flange above the Weld.

3. A method of making roof coverings from sheet metal on a roof covering support, comprising the steps of assembling successively strips of stainless steel of a thickness less than 0.5 mm. and having marginal flanges forming an angle with the body of the strips of less than 87 and more than 75 on said roof covering support, attaching a portion of an anchoring device in said support adjacent said marginal flange of one strip, engaging a flange of the first strip with an adjacent flange of a further strip and with a further portion of said anchoring device having said portions in displaceable relation to one another, pressing said adjacent flanges together by rolls while electric resistance welding them together to form a joint in spaced relation to the edges of the flanges and simultaneously welding said further portion of said anchoring device to said flanges, and folding over the parts of the welded flanges located between said edges and the weld to one side of one flange.

4. A method of making a roof covering from sheet metal on a roof covering support, comprising the steps of placing on the support a strip of stainless steel having a maximum thickness of 0.5 mm. and a marginal flange forming an angle of less than 87 and more than 75 with the body of the strip, attaching one portion of an anchoring device in said support and placing a further portion of said device in contact with said flange, mounting a further strip made froma similar material and having a marginal flange likewise forming an angle of less than 87 and more than 75 with the body of the strip but having a greater height than that of the first strip in close proximity to the first strip, pressing the flanges together while welding them by roll electrodes, the weld being placed in spaced relation to the edge of the lowest flange, and folding the highest flange over the lowest flange.

5. A roof structure composed of a roof covering and a roof covering support, the roof covering comprising strips of stainless steel having a maximum thickness of 0.5 mm. and each formed with upstanding longitudinal marginal flanges forming an angle of less than 87 and more than 75 with the body of the strip, the flange of one strip being joined with an adjacent flange of an adjacent strip by a weld spaced from the edges of said joined flanges, and the part of at least one flange located between the weld and the edges being folded to cover part of one side of the other flanges.

6. A roof covering as claimed in claim 5 and further characterized by the fact that one of the adjacent flanges is higher than the other and folded over the latter to cover at least the part of the latter flanges located between said weld and the edge of the lower flange.

7. A roof covering as claimed in claim 5 and further comprising an anchoring device consisting of mutually slidable members, one said member being secured to said adjacent flanges by the same weld as that connecting the flanges, and the other said member being attached to the roof covering support.

8. A roof covering comprising adjacent strips of stainless steel having a maximum thickness of about 0.5 mm. and each formed with a longitudinal marginal flange forming an angle of less than 87 and more than 75 with 6 the body of the strip, the height of the flanges of the adja- 1,882,105 10/1932 Wender 52-520 cent strips being equal, one of said flanges being joined 2,181,074 11/1939 Scott 52-572 with the other flange by a weld spaced from the edges of 2,546,839 3/1951 Theriault 52-11 said flanges and both flanges being folded over to one side 2,636,968 4/ 1953 Watter 287-18936 of one of the flanges. 5 2,745,523 5/1956 Biggs 52-521 2,910,018 10/1959 Rothfuchs et a1. 219-83 X References Cited 2,943,386 7/1960 Katz 219-83 X UNITED STATES PATENTS FOREIGN PATENTS 326,958 9/1885 Eller 52-520 932 743 12 /1 947 F 366,925 7/1887 Caldwell 52-520 10 220 391 /1924 Great i i 485,782 11/ 1892 Berger 52-521 517,963 4/1894 Patton 52520 FRANK L. ABBOTI, Primary Examiner. 631,092 8/1899 Reese 52-528 1,083,956 1/1914 Thomson 219-956 RICHARD COOKE Emmmer- 1,796,114 3/ 1931 Meadowcroft 29-548 15 JAMES L. RIDGILL, Assistant Examiner. 

1. A METHOD OF MAKING ROOF COVERINGS FROM SHEET METAL, COMPRISING THE STEPS OF USING STRIPS OF STAINLESS STEEL HAVING A MAXIMUM THICKNESS OF 0.5 MM., BENDING MARGINAL PORTIONS OF SUCH STRIPS THROUGH AN ANGLE OF LESS THAN 87* AND MORE THAN 75* TO FORM UPSTANDING FLANGES, PLACING THE STRIPS ADJACENT ONE ANOTHER WITH THE FLANGE OF ONE STRIP ADJACENT A FLANGE OF ANOTHER STRIP, PRESSING THE ADJACENT FLANGES TOGETHER BY MEANS OF PRESSURE ROLLS, ELECTRIC RESISTANCE WELDING THE PRESSED FLANGES TOGETHER WHILE PLACING THE WELD AT A DISTANCE FROM THE EDGES OF THE FLANGES, AND FOLDING OVER THAT PART OF THE WELDED FLANGES WHICH IS LOCATED BETWEEN SAID EDGES AND THE WELD. 